Visitors to the building could essentially tell time by observing the position of the shaft of light from the oculus, which crosses above or below the entry at noon. Furthermore, the beam hovers directly above the door at the March and September equinoxes, both moments of ceremonial importance for ancient Romans because it was then that emperors -many of whom cultivated an association with the Sun deity - were considered closest to the heavens and gods. The midday Sun on April 21 – the date commemorating the founding of Rome, as declared by Hadrian - spotlights anyone who stands in the open doorway of the Pantheon. The emperor would have entered the Pantheon at that very moment each year, the bright halo around him acting as a striking confirmation of his divine power and the glory of Rome. Emperors before Hadrian had focused their attention on the Sun, but it was Hadrian who demonstrated that he drew his authority from the solar source and could command in its name. As with the Egyptian pharaohs, his subjects believed he controlled its influence here on Earth.
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